/* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.camunda.spin.impl.util;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import org.camunda.spin.logging.SpinCoreLogger;
import org.camunda.spin.logging.SpinLogger;
/**
* Caches the initial bytes that are read from the supplied {@link InputStream} and
* allows to rewind these. As soon as more than <code>size</code> bytes have been read,
* rewinding fails.
*
* @author Thorben Lindhauer
*/
public class RewindableInputStream extends InputStream {
private static final SpinCoreLogger LOG = SpinLogger.CORE_LOGGER;
protected PushbackInputStream wrappedStream;
protected byte[] buffer;
protected int pos;
protected boolean rewindable;
public RewindableInputStream(InputStream input, int size) {
this.wrappedStream = new PushbackInputStream(input, size);
this.buffer = new byte[size];
this.pos = 0;
this.rewindable = true;
}
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
public int read(byte[] b, int off, int len) throws IOException {
int bytesRead = wrappedStream.read(b, off, len);
if (bytesRead > 0) {
if (rewindable && pos + bytesRead > buffer.length) {
rewindable = false;
}
if (pos < buffer.length) {
int freeBufferSpace = buffer.length - pos;
int insertableBytes = Math.min(bytesRead, freeBufferSpace);
System.arraycopy(b, off, buffer, pos, insertableBytes);
pos += insertableBytes;
}
}
return bytesRead;
}
public int read() throws IOException {
int nextByte = wrappedStream.read();
if (nextByte != -1) {
if (pos < buffer.length) {
buffer[pos] = (byte) nextByte;
pos++;
} else if (rewindable && pos >= buffer.length) {
rewindable = false;
}
}
return nextByte;
}
public int available() throws IOException {
return wrappedStream.available();
}
public void close() throws IOException {
wrappedStream.close();
}
public synchronized void mark(int readlimit) {
wrappedStream.mark(readlimit);
}
public boolean markSupported() {
return wrappedStream.markSupported();
}
public synchronized void reset() throws IOException {
wrappedStream.reset();
}
public long skip(long n) throws IOException {
return wrappedStream.skip(n);
}
/**
* Rewinds the stream such that the initial bytes are returned when invoking read().
*
* Throws an exception if more than the buffering limit has already been read.
* @throws IOException
*/
public void rewind() throws IOException {
if (!rewindable) {
throw LOG.unableToRewindInputStream();
}
wrappedStream.unread(buffer, 0, pos);
pos = 0;
}
public int getRewindBufferSize() {
return buffer.length;
}
/**
*
* @return the number of bytes that can still be read and rewound.
*/
public int getCurrentRewindableCapacity() {
return buffer.length - pos;
}
}